I don't think adding the read-only option is a good approach here. The recipe should rather support a custom-database option to provide the entire database snippet. With file storage, ZEO, RelStorage and various blobwrappers or storages for these, there's too many options that influence those.

It's actually much more explicit and clearer to write the entire storage snippets inside the buildout.cfg (with variable replacement for the directory base parts). Replicating the nested storage config in a set of flat buildout options is just confusing for any non-trivial case.

OK So that's a +1 from Elro (+1. It shouldn't be difficult to add, though it will adding in several places, once for each storage type. The recipe shows clear signs of organic growth over the years... ) and a -1 from Hanno :-)

Personally, I don't care whether I have to enter a "snippet" or whether I enter "read-only = true". The latter would be easier but if the former makes the most sense that's fine with me.